1. Field of the Invention
The present invention relates to an electronic device, and more particularly, to an electronic device in which electrical power required to operate a power supply system of the electronic device is minimized and a use time of a battery pack is prolonged.
2. Description of the Related Art
Electronic devices using a battery pack include a portable computer (such as a laptop computer, a notebook computer, a personal digital assistant(s) (PDA), and the like), a CD player, a video camcorder and the like. Electronic devices are generally used because they are handy to carry and can be used when a user is moving. Further, commercial alternating current is generally applied to these portable electronic devices by connecting an adapter.
The portable computer has been widely spread due to the development of the computer technique. Accordingly, a variety of methods have been developed to increase a charge capacity of the battery pack and to prolong use time thereof. Further, a method to prolong the use time of the battery pack having the same charge capacity same as the charge capacity of the conventional battery pack, (i.e., a method to prolong the use time of the battery pack) by minimizing electrical power consumption has been variously developed.
FIG. 1 is a control block diagram showing a power supply system of a conventional electronic device. As shown herein, a conventional electronic device has a system part 110 to operate a main function of the electronic device, a battery pack 100 and an adapter 200 to supply electrical power to the system part 110. A system power supply 111 outputs the system operating power by transforming electrical power supplied from the battery pack 100 or the adapter 200 into the system operating power to operate the system part 110.
The conventional electronic device further has a micro control unit 115 (MCU) controlling the system power supply 111 to supply/cut electrical power to the system part 110, a control power supply 112 to supply electrical power to the micro control unit 115 and a power selector 114 to output a system power selecting signal according to an operation of an user. Here, the MCU 115 turns the electronic device on/off by controlling the system power supply 111 to supply/cut electrical power to the system part 110 according to a system power selecting signal transmitted corresponding to the operation of the user. Diodes 121, 122 prevent currents of the adapter 200 and the battery pack 100 from flowing reversed.
However, in the power supply system of the conventional electric device, in order to sense the system power selecting signal transmitted from the power selector 114, the MCU 115 should be always turned on (i.e., electrical power should be always supplied from the control power supply 112). Thus, if the battery pack 100 supplies the electric power, the electrical power of the battery pack 100 is consumed without regard to use of the electronic device. For example, even if the battery pack 110 is 100% charged and the electronic device remains turned off, the battery pack 100 will be completely discharged after a predetermined time due to the power consumption by the MCU 115 and the like.
Moreover, where the MCU 115 has a memory such as an electrically erasable and programmable read only memory (EEPROM) to store information whether the electronic device is turned on, the MCU 115 consumes a great deal of electrical power, thereby increasing power consumption of the battery pack 100.
Further, the power supply system of the conventional computer causes frequent charge and discharge of the battery pack 100, thereby shortening the use time of the battery pack 100. If the adapter 200 is used, the problems described above are not caused, but electrical power is also unnecessarily consumed to store the information of on/off states for the electronic device.